I am a newbie to Arduino. I have a Maytag Neptune washing machine motor along with the power supply and MOSFET driver circuitry. This Switched Reluctance Motor is a 3 phase 12/12 device. I would like to control the motor using my Mega 2650 and I am looking for some help getting started with the code. My goal is to just get the motor rotating and then work on on fine tuning various aspects such as speed adjustment, regenerative braking. etc.
I know that rotor position can be determined using sensorless techniques however to keep things simple I am prepared to use Hall Effect sensors.
Has anyone had success controlling a SRM with an Arduino
Interesting project. I'd first measure the winding resistance and choose an operating
voltage where the winding resistance prevents excessive current, makes for less chance
of over-current damage.
Conceptually a SRM is very similar to a 3-phase stepper motor, you can just sequence
each phase in turn (if the current is limited by resistance, that is).
Once you go up to the design voltage of the motor you will need to monitor the current
since you need to drive the winding until the current reaches its maximum (before
full saturation of the poles) and no further. Thereafter you may have to drive the winding
in reverse to reduce the current to zero at the end of that phase's cycle. Or put another
way the winding's inductance is dominant and limits the rate of current change.
If you drive each winding in turn you only have to monitor the overall current to the
power stage, since only one phase is carrying current at once (at low speed certainly).
For efficient high speed operation the ramping of currents for the phases will probably
overlap, meaning 3 current sensors are needed.
You'll need faster ADCs than the Mega's built-in one, perhaps current sensing would
be better done with DAC+comparator circuit - you program a current limit and send
it to the comparator - the output of the comparator goes to an interrupt-enabled digital
pin to allow fast response in the code.
Another thing to note is that the direction of current isn't important, so each phase
(if brought out as two wires each) can be driven with a half-H-bridge, using the free-wheel
diodes to conduct during current-ramp-down. A full H-bridge for each phase might allow
more flexible control (regen braking??)
Thanks for your advice. I have attached a schematic of the "C" phase for the Mosfet driver circuit (courtesy of "theprohectasylum.com") . Tomorrow I will measure the stator coil phase resistance and disassemble the motor to verify if the four (4) coils associated with each phase are series or shunt wound. I suspect they are in series but while I have the motor apart I will attempt to bring each coil lead out through the stator housing so I can change the phase coil configuration between series and shunt.
